At emission-relevant automotive control devices diverse methods of detecting faults are carried out for statutory reasons. On the one hand, many methods are a direct legal requirement and in most of these a fault has to be detected and the driver has to be alerted by means of a malfunction indication lamp if a specific emission limit is exceeded. At a data communication interface for the workshop codes, such as for example DTCs (diagnostic trouble codes), for each detected fault are made available in order to facilitate fault diagnosis.
In previous systems, such as are known from the background art, the fault detection of each individual method is independent of the fault detection of the other detection methods. For example, a problem regarding the injection quantity of an individual cylinder is only identified as an emission-relevant fault if this problem alone already results in the emission limit being reached. In other words, it is only when one of the cylinders exceeds the defined emission limit value that a fault is detected. If, however, the problem is less serious in terms of emission deterioration, then no emission-relevant fault is detected and/or communicated to the driver. If in the latter state there are further non-serious faults for example at one or more of the other cylinders, the overall system possibly exceeds emission limits but none of the individual methods detects an emission-relevant fault. In other words, in the situation where none of the individual cylinders exceeds the emission limit value but all of the cylinders combined exceed the emission limit value, this is not detected as a fault.
From DE 102 57 686 A1 moreover a method of adapting an injection characteristic is known. Here, an injection valve characteristic of an activated fuel injection valve that represents a reference injection behavior is adapted to ageing-related changes of an actual injection behavior. Here, during an operating state that requires no fuel injection, the injection valve is intermittently activated. In this case, at least one working cycle with activation precedes a working cycle without activation of the injection valve. In this case, in each case a rotational speed value of the internal combustion engine is detected for the working cycle with activation and at least one such value for the working cycles without activation. The difference of the detected values is then used to carry out a correction of the injection characteristic.